Yumemiru Otome 3

Mizuki has been fucked by Tanabe for two days under the promise that she will delete her sister's indecent videos. Mizuki accepts Tanabe even though the birth control pills he gives her are making her sick... One day, Mizuki is taken outside and witnesses an orgy with many men, including her beloved sister, who is also a student at the school. One of them was her beloved younger sister, Aika...?